Apparatus for making precast concrete units



Jan., W, 1950 A. HENDERSON APPARATUS FOR MAKING PRECAST CONCRETE UNITS 4 Sheets-Sheet l Filed March 27, 1946- Jan. 17, 1950 A. HENDERSON 2,495,100

APPARATUS FOR MAKING PREcAsT CONCRETE UNITS Filed March 27, 1946 A4 sheets-sheet 2 A. HENDERSON 2,4%,l00

APPARATUS FOR MAKING PRECAST CONCRETE UNITS 4 Sheets-Sheet 5 Jan. 17, 1950 Filed March V27, 1946 79 55 fl'gl. 79 a @Q fw] .yarn 17, 1950 A, HENDERSON 2,495,100

APPRATUS FOR MAKING PRECAST CONCRETE UNITS Filed March 27, 1946 4 Sheets-Shea?I 4 INVENTOR Patented Jan. 17, 1950 maant SGFVGR MAKING PRECAST CONCRETEi UNITS Allert. Henderson, Pittsburgh, Pa., assigner, by

mesne assignment-,Sto TheCemenstone Cor-- lmration,` Pittsburgh, Pat, a' corporation of' Pennsylvania' Application Marchl, 1946,.,SeriaI.No,- 6573497 This invention relatesfto. the.v manufacture.. of.` precastv concrete units; for use. inbuilding. conf struction and, in-particular, toa gang, mold providing a plurality. of mold cavities wherebya number of units-may: be cast at one time.

It has not4 been possible.- heretofore. to. achieve the economlesiof masseproductionin. the. manu:- facture of; precast concrete structural units. for several reason-s. Inathe` first place, theemold walls required for. making units such as panels having heights as great as and lengths as great as 5.0i( are so heavy that it-.isdiiicult to handle them in placing them in and removing. them. from.` the mold. and to keepl them plumb therein. This handling.V difficulty makes the. operation slowand costlyandincreases the: likelihoodY of damageto green concrete units. The handli-ng. ofthe-units themselves, when. cast, furthermore, requires. nu* merousv overhead; cranes.` of long l spank and 4large capacity which-.are quite costlyf. v

I. have invented ai novel-apparatusfor. molding concrete, units whereby the` atorementioned. ob..- jections are overcome or minimized.' Inra preferred embodiment, I provide elongated?. gang molds. with small, low mobile. cranes..str.addling them, each crane having` hoist meansadaptedto lift. the: sidewalls andv pallets or. bottom walls forming. the molds. andthe units. cast. therein. The cranestravel alonglttiemoldsandthe. hoist means travel alongthe. cranes,v The mold members may thusy be suspended.` from thecranepen.. dulumwise. This facilitates. control Aandlhandling of the mold Walls to keepthemplumb. The1 mold walls may also be.' easily clamped together while they are, suspended. Thependulum action. of the suspended wallsA facilitatesremoval of.' the products made. in themoldssince it permits the Walls. to swing clear of themolded concrete units; This. is ofparticular importancewhere. the. mold .wallforms are of the heightandlength. above- 'forms of steel; for example, in proper relation and alinement. The prestre'ssing4 off'the reinforcirig..`

12 Claims'. (CIL 25T-12T) makes the moldwallsiiexible and' prevents 'cracks since. the concrete is in compression-as a result of the prestressin'g. This allowsthe form' to bend slightly, if. desired, without cracking so that'warping caused by heating. means embedded' in the walls will'not damage them. Infact, such walls may be cast in relatively great widthsand lengths without danger of injurious. warping4 and their cost" is considerably lessthan that` ofisteelv molds for such large sizes;

I make special. provision for sealing' the joints between the side walls and palletsor'bottom walls of the molds'. Iieakage through these'join'ts is a serious. problem. because of the height of the column of; concrete which is quiteuid when first poured. l"provi i`eu a sealingV gasket including' a stainless. steelspring strip and a rub-ber contact strip secured to onemoldim'ember. and' extending toward a cooperating' member; the contacting strip extending beyond the spring strip. The

`spring strip has' slits closely spaced therealong whereby the portions' between adjacent' slits act as spring4 fingers to press the contacting strip into en'gagement'withthe adjacent' mold wall;

Ialso provide camberL-forming members removably attached to the mold side walls. and to the top of 'the mold bottom walls for the purpose of making; members having, a depthv varying from point-tofpoint; along the length thereof.. Il also provide on the upper, outer corners of the mold side Walls a metal member having holes spaced thereal'ong. Crosslties may be secured to these members. by'bol'ts for .securing bolts; pipe lengths, nuts -or the like* to be' embedded in the concrete members. The metal members also serve for removably securingv bevel-forming` strips'. attachable 'toi tlieupper edges ofthe moldsidewalls andthe camber-formi'ng members. referred to above. Certain precast concrete units'` such as columns have' allf'our corners beveled' while in the. case of beams', the bottom" corners` only are beveled. Both typesV ofr members; m'ay'easily be made in the same molds by means' ofthe` aforementioned detachable bevel-forming strips.

The mold' side Wallsand'pallets. are disposed on a' casting bed' having prestressecl reinforcing and heating meansembeddedrtherein. as' well as means' for clamping, the moldlwalls and pallets together. Instead of a casting bed, I may employ spaced cradles for supporting the pallets and mold walls with suitable. clamping .means for securing them thereto.

Itis desirable to' prestress the reinforcement of certain structural units such as thin wall panels toprevent cracking. For-this purposaprovide a frame having spaced detachable and slidable pulleys adapted to be placed on or about a mold so that a wire may be passed back and forth over the pulleys and tensioned uniformly throughout before being embedded in the concrete.

A complete understanding of the invention may be gained from the following detailed description which refers to the accompanying drawings illustrating a preferred embodiment and modifications. In the drawings,

Figure 1 is a partial transverse section through a gang mold composed of a casting bed and spaced side walls disposed thereon;

Figure 2 is lan end elevation showing one of the mobile cranes cooperating with the casting bed and the pallets and mold walls thereon;

Spaced reinforced concrete mold walls I3 rest on the bed I and have prestressed reinforcing bars I4 embedded therein and a pipe I5 for conveying a heating fiuid or receiving an electric heating element. The walls have integral, laterally projecting core portions |30.. Metal channels I6 are anchored to the top and bottom of the walls I3 ,to provide armor for the concrete and metal angles I7 are secured to the exposed corners of the core Figure 3 is a perspective and transverse secf tional view showing mold walls and pallets supported in spaced cradles;

Figure 4 is a partial section similar to Figure 3 showing supplemental mold walls adapted for the formation of a girder having shelves along both sides thereof;

Figure is a partial section and perspective view of a mold side wall having a bevel-forming strip detachably secured to the upper edge thereof;

Figure 6 is a partial transverse section through a mold having its interior side walls integral with the pallets thereof;

Figure '7 is a partial elevation of a channel adapted to serve .as armor for the upper edges of the mold walls;

Figure 8 is Ia transverse section therethrough taken along the plane of line VIII-VIII of Figure 7;

Figure 9 is a central section through a plug `adapted to be threaded into holes in the channel of Figures 7 and 8;

Figure 10 is an elevation of a mold wall hav- .ing camber-forming means secured to the upper edge thereof;

Figure 11 is a transverse section therethrougl taken along the plane of line XI-XI 0f Fig- Aure 10;

Ishowing the sealing strip closing the joint therebetween;

Figure 15 is a partial elevation of the metal spring strip forming part of the sealing means;

Figure 16 is a view similar to Figure 14 showing a modified construction;

Figure 17 is a partial transverse section through a mold wall similar to those shown in Figure 1 with a modified form of mounting for the strips forming the tongues and grooves in the edge faces of the units; Y

Figure 18 is a partial section similar to Figure 1 .showing a further modified form of mold side lwall; and

Figure 19 is a diagrammatic elevation showing an arrangement of pulleys on a supporting frame for prestressing reinforcing wire to be embedded in a unit such as a panel.

Referring *in detail to the drawings and, for the present, to Figure 1, a precast concrete casting bed I0 has prestressed reinforcing b-ars I I embedded therein and a pipe I2 for conveying a heating uid or receiving an electric heating cablef' portions I3a for the same purpose.

It will be apparent that the walls I3 and their core portions |30I are shaped for the molding of precast concrete structural units of H shape.

`End walls I8 are positioned between the walls I3 -at desired intervals. The end walls are simply lengths of H-shaped structural units of sufficient -weight to withstand the end thrust applied, when clamped between the walls I3 by means shortly to be described. The walls I3 have upper and lower rubber strips I9 and I9 shaped to form tongues and grooves along the edges of the flanges of the H-shaped units cast between the walls. A metal plate I9a secured to the upper channel I6 extends over the edges of the strips I9 to protect them. The lower strips I9' have bevel-forming projections at the foot thereof. These strips are so dimensioned that they extend below the bottom channels I6 when the wall I3 is lifted from the bed I0. Thus, when the wall is lowered onto the bed, the strips I9 are compressed to form a gasket seal.

The pipe I5 and armoring channels I6 and 'angles I'I of the mold walls may be prestressed as well as the reinforcing bars I4. This makes the walls more exible and lessens the danger of cracking in case the walls are wedged or clamped together slightly out of parallelism. It also prevents cracks which might otherwise result from repeated heating and cooling of the walls or the wetting thereof to prevent dehydration of the units, or the shrinkage which occurs in concrete members in the early stages of their life.

Y A plurality of the walls I3, when properly placed on the bed ID, with end walls I8 therebetween, vmay be clamped by screws 20 threaded through posts 2I extending upwardly from the bed. The bed has armoring channels 22 along vits side edges and the posts 2l are secured thereto by anchor bolts 23 set in the bed. Water pipes 24 are embedded in the walls along the tops thereof. Nozzles 25 are spaced along the pipes to discharge water onto the units cast between the side `walls to prevent dehydration as curing proceeds. Additional pipes 26 are embedded in the core portions I3a of the walls I3 and have nozzles 2'I spaced therealong adapted to discharge jets of air tor water under pressure to assist in breaking the `bond between the walls I3 and the units cast therebetween when it is desired to remove the latter from the mold. A similar pipe 28 having nozzles 29 spaced therealong delivers jets of air or water under pressure between the walls I3 and the bed vIl! to lift the walls slightly should it be desirable to move them by hand in adjusting them to the proper position on the bed. Connections are made to the pipes I5, 24, 26 and 28 by V4flexible hose. Yokes 30 extend through the plate ISa and upper channel I6 and have their ends embedded in the walls I3, to receive crane hooks for lifting the walls.

Figure 2 shows the bed I0 equipped with spaced `mold side walls 3| and shorter length pallets 32 therebetween. Mobile cranes 33 straddle the bed,

the mold walls, and the curing or storage area. Each crane comprises legs 34 having wheels awed-roo' traveing*alongrailsali* and spaced cross beamsrn 36 and 31. Hoisting means 38 for the sidefwalis 3|v travel along the beam 361whilefhoisti-ng means 39 for thepallets32l travelA along beam 311. Usual`- ly it` willbe-found convenient toeemploya pair` of cranes; or everr more; With-atleast' one adjacent each-end of the gang mold-1 The hoisting means 38 may convenientlyftake the formof turn-lm buckles while the hoisting means 39 are pre-feit# ably chain blocks. Both types1^ of hoistingfmeans engage eye-bolts 31a* extending throughthe up per armoring channels Sib" and 32`bofth'e walls* and pallets; Power-driven hoisting'means may; however; bel used instead of'manually operatedv means: Thev hoisting' means* 39'- preferably have detachable links' 39d" for lifting the pallets 32;4 These links arefremoved whenitheshoisting means arefemp'loyed for lifting the structural'funitsfcast in' the mold;

The wallsf3 l are offprecast reinforcedconcrete,= the reinforcing beingprestressed, andihavezarmor atv the top and-bottomin the form of-metal' channels.. They also have pipe' lengthsv embedded therein fof conducting-t-'aheatingf fluid. Thefpal-t lets' 32 arev of' generally similar construction;` Members of various depths may be molded by blocking up theA pa'llets'to the desired height. Rubber strips' lif'carried by the pallet servethe. double function offseal'ingtheljoints-betweenf the pallet' and mold walls and" forming a bevel at each bottom corner of' theunits east'in the mold Itwill beunderstood`thatthe side walls 31" need beA raisedionly slightly fromthe bed Ir to permit them to be moved sidewise'. TheY units marde in themold, however, have to besliftedabovethe level ofthe top' of th'elsid'ewalls' ifthey are to be moved sidewise. The walls, pallets=or mold units; however, may be shifted longitudinally as 'well' as transversely, when lifted,A byV moving the'cranes along the rails'3'5l orbyj moving' the hoists along the cross beams Stand 3T.

In the case `of wall-panel unitsfhavinga-height of: as much as IW; it is'desirable yto remove them endwiseV from the molds because of'V their considerable height whencaston' edge". I'nl stripping such units from the mold,` one side wall isfrst removed by lifting itfsligh-tlyffwith the. hoisting means 38. Whensus-pended"pendulumwise; the Walls are easily' moved sidew-iseto release'a plu'- rality of units at one time. Instead of leaving the units in the mold untill fullyhardened, I may strip-the mold wallsfrom theunits whilethey 'are still green andcarry them away on the` pallets', thereby freeing'the mold for use-with additional pallets.

The cranes 33 mayIiave-water-spray means mounted thereonV for wettingdbwn the uni-tsI or the molds. Similarly, oil-spray meansmaylbe mounted on the cranefor ciling them'olds. The cranes' may also provide supportV for 'magnets for lifting the' mold walls', vibrators, screedsgtrowels, vacuum-lifting means-for removingthefhardened units and a hopper for distributing concrete evenly*alongtheA length of the molds;

In removing the'units made in tlie=mold's, the mold walls and pallets may be lifted all at once orindividually or a separatehoisting means-may be employed for removing the concreteunitsl from the'V molds'.l The mold walls are preferably clamped together whileA suspended just sufliciently to swing clear of the bed. Concrete may be poured into the molds Whilethey` are thus suse p'ende'dv and clamped together. Ify desired',` the cranes'may travel onrails transverseto the-length wouldfi permitfsidewise-removalv ofthe cast'f units to position laterallyi'of the Abedifor further cur-` ing f on'storage-s- IFigureB shows* aprecastconcrete cradle 4i resting ona-v'foundation'; The cradle comprises a horizontal=portion-'Mw and-si'deposts.llb. A plurality of suchcradle's in spacedfl relation support spaced mold walls 3|' and are straddled by cranesfsuch' as that shown at313 The walis3l' arersimilar7 tolthe Walls v35| but areprovided with a sheathing' lid-"ofTV stretched tliin stainless steel bent therearound under tension and4 having its edges secured? together by a channel 'fili-and4 its ends securedt'otheendsofthe mold' walls. Pali lets 312iJ generally siinila-r to those shown at 32 are disposed'- between the` side walls and are spaced upwardly from the cradle by blocks i5 for molding units-y of desired depth. The-side Walls andpallets'are-clamped together' by wedges di? driven between one of the sideposts of: the cradle' and theadjacent side wall.

Anglejbarsf 41 havingv` holes spaced therealong are-securedto the Youtside mold walls adjacent their'V upper* edge; Bevellforming strips,` Gamberforming elements and other associa-ted? elements maybe securedj inl proper' relationto the meld wallsk byv bolts inserted through the holesin the angle bars 4". Pins dprojecting fronithe' cradle providefulcrums for bars employed tofraise the side walls and pallets/dfi thefmoldsz Figure' 4r' shows apair of supplemental side walls E9' adapted to be connected to sidewalls 3 I. The side Walls 49 are-shaped to lforni a--girder having a shelf along each sidethereof. Additional supplemental side walls- 5:0' resting on' the side walls' 49 permit theY height` of' the girder above theA shoulder'to be varied as desired. Eye bolts 5I are embeddedin the' laterally-projecting shouldereformingjportionsof the side walls to facilitate'the' handling-'thereof by the cranes' 331 The' sidewalls 49* areV secured to `the walls 3 iJ by vsplice"plates 52 secured by' screws to'v the channels armoringthe meeting edges of the walls. The 'supplementalside walls 56- are similarly secured Figure-5 shows aside wall`3fl provided withv a bevel-forming memberr 53' extending' along the upper edge thereof Thef-beve-l-iorming member' is a channel having one'ange shaped'asI ati 54 to'lform a bevel at the-upper' corner of the unit ycast against the' wall 3l. Clamping screws 55 extend through the'otherfla-nge of the channel andgrip the armor channel onthe upper edge Vof the side wall. It willbeunderstood thatone of the bevel-forming members 53. is applied. to each side w-alllof"y a mold in which'lis to be cast ai unit having all itscorners beveled.

Figure 6 shows a mold composed of. an outer side. walll 3I and an inner member including a side' wallfand a pallet having. portions 55a extending outwardlyfrom both sides ofv the wall. The pallet portions 56a of the wall fhave armor plates 51 thereon and` an armor plate' 58 extends over the entire bottom thereof. A rubber gasket and bevel-forming strip 59 seals the: space be,- tween the wall 3| and the adjacent pallet portion 56a. A pipe 60 is disposed in. said space With nozzles adapted to direct jets of air between the structural unit Bil' cast' on the palletY and the side wall 311, whileV the concrete is still plastic or during the actual filling of the mold, to remove surplus'- air and water accumulating.. on the. side walls as a result of vibrating. the mold, which would" otherwise leave pin-holes inthe surface of'tlre moldsjinst'ead of parallelthereto;v "T5-of' theuni't. Whenair underpressureis-admtted to the pipe 60, the jets therefrom displace the free edge of strip 59 slightly and flow upwardly along the side walls 3|, thus sweeping upwardly any air or water accumulating adjacent these walls. The jets cause slight separation of the freshly poured concrete from the mold walls sufficient to release air and water trapped in pockets therein.

The unitary pallet and wall member 56, 56a makes possible the removal of a pair of concrete units from the mold at the same time. Eye bolts 62 are threaded into nuts 63 for this purpose. The nuts are disposed in a slot 63a in the upper edge of the walls 3| and 56. The eye bolts are inserted through holes in the upper armoring channel of the walls. By this arrangement, the cranes may be attached to the side walls at any point therealong. The unit 6| has coupler nuts 64 spaced therealong and threaded onto anchor bolts embedded therein to accommodate eye bolts 65 for lifting the member. The nuts 64 may be tapered to permit their removal for further use. Figure 6 also shows the slot 66 in the upper edge of the side wall 3| to accommodate nuts for receiving eye bolts.

Figures '7, 8 and 9 show the armoring channel 3|b for the side walls having holes in its flanges for the screws securing the splice plates 52, and holes in its web for admitting the eye bolts 3|al and 62. These holes are normally closed by plugs 61 threaded therein. The channel also has anchor bars extending downwardly therefrom adapted to be embedded in the side walls 3|.

Figures 10 and 11 show camber-forming members 68 in the nature of dash-boards secured to the upper edge of a side wall 3|. These flash boards permit the molding of members having a depth which decreases from a maximum at the center toward each end. The flash boards are sectional and are secured to the mold wall by screws threaded into the holes in the webs of the armoring channels 3|a, 3|b. The flash-boards 68 may be of such shape as to permit the molding of units having a steep slope toward each end. For example, a beam 50 long may be made 36 deep at the middle and only 18" deep at each end. This provides a beam of reduced weight without sacriiicing its load-carrying capacity.

Figures 12 and 13 show a supplement pallet 69 adapted for molding a member having a depth increasing from a minimum at the center toward each end. This pallet is generally similar to the pallet 32 and is adapted to be laid thereon but slopes downwardly toward each end from a high point in the middle. The supplemental pallet 69 is formed in sections like the ash boards 68.

Figures 14 and 15 show a modified form of gasket for sealing the joint between a mold side ywall 3| and pallet 32. It comprises a strip 1| of metal bent to an angle and slotted along its length as at 12 providing spring iingers to which is cemented a rubber sealing strip 13. The strip 1| is secured to the pallet 32 by bolts fastened to the flange of the upper armoring channel 32h thereof. The outer edge of the strip 13 engages A the surface ci the wall 3|. In addition to sealing the joint, the strip 13 acts as a bevel-forming means.

Figure 16 shows a modied sealing gasket and bevel-forming member comprising a deformable rubber strip 14. A pipe 15 embedded in the pallet 32 is adapted to admit fluid under pressure behind the gasket through holes 16 in the flange of the armoring channel 32h. When fluid pres- .'sure is thus applied, the gasketis forced into sealing contact with the adjacent surface of the Wall 3|.

. Figure 17 shows a modified side wall |3 having channels 11 secured to the flanges of the upper armoring channel I6 to accommodate removable tongue-and-groove-forming strips 18. This construction permits easy removal and replacement of the strips 18 when worn or damaged.

Figure 18 shows a further modified form of mold wall 19. Each mold wall comprises a pair of concrete slabs 8|] with a rubber sheet 8| disposed therearound. This sheet may be thick enough to have electric heating elements ernbedded therein for connection to a suitable source of current by a cable 82. Concrete sticks to cold rubber covers but will not stick to a hot rubber cover. The slabs 88 are separated by an upper spacer 83 of T-section and spreader pins 84 forced upwardly between the slabs by wedges 85 resting on the bed Ill. The lower edges of the slabs slope inwardly and upwardly as at 86 whereby the slabs tend to tilt toward each other about their lower edges when the spacer 80 is raised and the wedges removed as indicated at the right-hand side of Figure 18. Gasket strips 81 may be removably disposed between the pallets and side walls by hand or may be cemented to the pallets and side walls.

Figure 19 shows a means for prestressing a reinforcing wire adapted to be embedded in a molded concrete unit such as a wall panel. A frame 88 is adapted to be disposed on or around the mold for the concrete unit and is provided with pulleys 89 spaced along the sides and ends thereof. A reinforcing wire 90 is trained over the pulleys 89'and is looped back and forth crosswise and longitudinally of the frame, the ends being secured to tensioning means 9|. A single tensioning means will suffice, however, if one end of the wire is xed to a suitable anchorage or both ends of the wire may be secured to one tension means. By tightening up one or both tensioning means, the reinforcing wire may be stressed to the desired value. The concrete is then cast in the mold, embedding the crisscrossed portions of the wire, and after the concrete has set suiiciently to develop a iirm bond with the wire, the exposed portions thereof are cut oi.

It will be apparent from the foregoing that the invention is characterized by numerous advantages over methods and apparatus previously known for making precast concrete units. The molds may be kept suspended and clamped together and lled and vibrated while suspended but YI prefer to set the gang mold side walls on the casting bed. If the gang mold side walls have pallets disposed therebetween, I prefer to yset the gang molds on spaced cradles and suspend the mold side walls only during the removal of the concrete units from the molds. Alternatively, I may suspend both the mold side walls and the pallets, as well as the concrete units during the removal of the concrete units from the molds. Y f -During the unloading operation, I may unhitch the gang mold side walls and hook onto the concrete units and move the crane or cranes with the concrete units suspended thereon to a Idipping pool or storage area. I may unhitch the pallets with the green concrete units resting thereon and move the crane or cranes having suspended therefrom the gang mold side walls v to another casting area so that they can beused geen o o :more frequently f I may yunhitch .theggan-g mold sidewallsland move V.thx-:serene` or icranes .with the suspended pallets and -.-the green...concretefr.est ing `thereon 4away fromithe side walls; for f urther curingiof the greencconcrete units adjacent the molds anduunder' thesmobi-lercranes orelsewhere. VOther pallets may y.thenffbep1-amen ybetween the side Walls-When the ypallets previously used are engageidby the green sooner-ete units remaining vthereon for curing. 1I .may use vacuumcups .to lift `the.concreteau-nits `instead-:of ,theeye bolts.

The hoisting :means: attached tothe .pallets are used to raise and yflower them .s,o that blocking can be inserted under y)them to any depth required of the mold. I use precast concrete for the end walls of `V:the V:mild tand 'their ggreat Weight, withthe clamping of the mold walls, assures that 'they will not move duringthe casting operation.

I may attach a hopper, vacuum-liftmeansyvibrators, rorvascreed `Aand trowel vto one of the mobile-cranes, then unhitchthe hoistingr means from the .gang mold members and. use the mobile y.crane to 4fill the ml'ds with a cQDcreteIniX. The vibrator .serves to compact the concrete ,uniformly and the screed arid 'trowelprovide means 4for smoothlylevelling offthe concrete at the top of the gangmolds. I may use internal vibrationlin which .case spaced vibrators attached to the mobile crane could easily'be'lowered 'into .the molds and give an accurate .anddenitewibration-at every inch along'thelin'terior ofthe `con- .-.crete while it is 'being pouredintothe gangmol'ds. nInterior .vibration is'best on Slarge heavy precast concrete structural units. `I may attachtto ,the

travelling or mobile crane a water sprinkling means for wetting the concrete units in the molds, and I may attach an oil-spraying means to the mobile crane for applying oil to the interiors of the molds. This assures complete oil coverage of the mold Walls. with a hopper, vibrator, screed and trowel, vacuum-lift means, water and oil-spraying means attached thereto may be the subject of a separate patent application.

The mobile cranes straddle the gang molds and run on rails parallel to the gang molds. The cranes may be wide enough to unload the concrete units beside the gang molds or they can move beyond the gang molds to a curing or storage area. wide enough, I can remove the mold side walls to a position beside and parallel to the mold for reuse while the green concrete units molded between the side walls are left where cast for quicker curing. Then, While the sets of side walls are in use, the mobile crane can be used to remove the cured concrete units.

The concrete mold members are armored to prevent chipping and have embedded therein means for wetting the concrete units cast therein. Means are provided for breaking the bond of the units to the molds. The mold members have pipes embedded therein for conveying a heating fluid, Iand I may dispose therein electric heating cables. In a modification, I cover the mold Walls with a rubber sheet having electric heating wires embedded therein, and I may cover the rubber sheet with a layer of material to absorb the surplus water and air from the concrete mix in the molds so that dense uniform attractive surfaces are formed on the precast concrete units. The removal of the air and water also removes pin and air holes which mar the surfaces of precast concrete units.

In a further modification, I stretch stainless The mobile crane Furthermore, by making the crane y l fvsteel sheets across ,the aces of .the mold walls clamp fthe sheets to the .Walls ,under great tension to removaalllkiriksltherefrom.

I also ,providerubber VYgasketsand means for pressing themagainstithe mold walls toseal the joints therebetween. In .one vform vI cement va rubber gasket to two mold wallsat `their joints sothat aperfect leakproof jointlisassured.

The wire placed .under tension while .in the moldmay be vibratedduring'the casting voperation. The vibratingof lthe stretched wire sets .up lasremarkable action which ;he`lps in settling the concrete andalsoallows the .cement particles to settle around the wires more Vdensely,.thereby providing a bet'ter :bond between the concrete and the wire. This v"dense cement coverV protects the Ith'in wires againstgrusting.

I claim:

1. 'Apparatus .or ,making cementitious structural units comprising a moldlhaving spaced side `walls and a bottom wall disposed therebetween, A.gasketsfcr sealing thejointsbetween said spaced Vmoldsi'de wallsandcsaidbdttom wall, each com- ;.prising asheetrmetalstrip. secured to said bottom Wall, Ythe sheet metal strip. projectingbeyond the said mold bottom wall, the projecting portion of saidsheet metal .strip'jhavlng a series of closely spaced slits therein, and a, strippf resilient materia'lsecuredto the topiosaid slitportion of said metal strip, said strip .of resilient. material pressing againsta moldside wall.

T2. Apparatus for .making .cementitious struc- .tural units comprising a moldhaving .spaced walls and -a camber-formingmernber `detacha'bly .se- A cured Vto the top of .each ofsaidmoldwalla .each

of said camber-forming members being of gradually increasing height from an end thereof toward the mid-portion thereof and being sectional, each section thereof being tapered in height with the higher end of one section matching the shorter end of an adjacent section so that by appropriate selection of sections camber-forming members of desired length may be formed.

3. Apparatus for making cementitious structural units comprising a mold having spaced walls and a bottom wall disposed therebetween, and a camber-forming member detachably secured to said mold bottom wall, said camper-forming member being of gradually increasing height from an end thereof toward the mid-portion thereof and being sectional, each section thereof being tapered in height with the higher end of one section matching the shorter end of an adjacent section so that by appropriate selection of sections a camber-forming member of desired length may be formed.

4. Apparatus for making cementitious structural units comprising a mold having a wall, and means embedded in said wall terminating at the mold surface for wetting the cement units molded against said wall.

5. Apparatus for making cementitious structural units comprising a plurality of mold side Walls, means for suspending said mold Side Walls, a plurality of mold bottom walls disposed in sideby-side relationship and between said mold side walls and means for suspending said mold bottom walls.

6. Apparatus for making cementitious structural units as defined by claim 5 characterized by a support for said mold walls having means for clamping said mold side walls against said mold bottom walls.

7. Apparatus for making cementitious structural units as defined by claim 5 characterized by a frame on which said mold Walls are suspendable movable parallel to said mold walls and on which said mold walls are movable sidewise.

8. Apparatus for making cementitious structural units as dened by claim 5 characterized by `saidy bottom mold walls being attached to some of said mold side walls.

9. An apparatus for making cementitious structural units comprising a mold having spaced Vertical side walls and a bottom Wall and means embedded in and terminating at the surface of one of the Walls for forcing a fluid between the bottom Vwall and one of the said side walls.

10. Apparatus for making cementitious structural units comprising a mold having spaced side walls and a bottom wall, said side Walls being separable from said bottom wall, a gasket for sealing at least one of the joints between the side and bottom Walls, said gasket comprising a sheet metal strip secured to and projecting froml one of said walls, the projecting portion of said creasing height from an end thereof toward the mid-portion thereof and being sectional, each section thereof being tapered in height with the higher end of one section matching the shorter end of an adjacent section so that by appropriate selection of sections camber-forming means of desired length may be formed.

12A. Apparatus for making cementitious structural units comprising a plurality of mold side Walls, means for suspending said mold side walls, a plurality of mold bottom walls disposed in sideby-side relationship and between said mold side walls and means for suspending said mold bottom walls, at least some of said means including adjustable means to enable varying of the relative elevations at which said mold side walls and said mold bottom walls are suspended.

ALBERT HENDERSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 943,991 Nelson Dec. 21, 1909 1,096,792 Mumford May 12, 1914 1,140,785 Williams May 25, 1915 1,180,472 Clark Apr. 25, 1916 1,415,649 Jagenburg May 9, 1922 1,830,225 Dance Nov. 3, 1931 1,917,062 Reinhard July 4, 1933 2,148,084 Nock Feb. 2l, 1939 2,296,553 Heritage et al Sept. 22, 1942 2,270,541 Martin Dec. 20, 1942 2,306,107 Henderson Dec. 22, 1942 2,334,804 Atterbury Nov. 23, 1943 2,408,149 Miller Sept. 24, 1946 

